Screen and projection system

ABSTRACT

A screen includes a plurality of reflecting portions disposed on a flat surface with a clearance left between one another. The reflecting portions reflect diagonal incident light coming in a predetermined direction other than the normal line direction of the flat surface, and block the diagonal incident light by reflecting the incident light such that the incident light cannot reach each area between the adjoining reflecting portions on the flat surface.

This is a continuation of application Ser. No. 11/869,434 filed Oct. 9,2007, which claims the benefit of Japanese Patent Publication Nos.2006-279506 and 2007-203867 filed Oct. 13, 2006 and Aug. 6, 2007,respectively. The disclosures of the prior applications are herebyincorporated by reference herein in their entirety.

BACKGROUND

1. Technical Field

The present invention relates to a screen and a projection system, andmore particularly to a technology of a screen used in combination with aprojector which projects light from a position close to the screen.

2. Related Art

A reflection type screen used in combination with a so-called frontprojection type projector needs to have high reflectivity to produce abright image. This type of screen is further required to have highdiffusibility sufficient for diffusing light to a desired area to obtainpreferable visibility angle characteristics. A technology for obtaininghigh reflectivity and high diffusibility of the screen has been proposedin JP-A-58-52628, for example.

Recently, a projector capable of achieving close projection has beenproposed. By the function of close projection, the projector can displayan image on a large screen from a short projection distance. During theclose projection, the projector applies light having a large incidentangle to a screen. A screen in related art has a flat surface or asurface having small concaves and convexes to which paints in white,silver, or other colors are applied, for example. When light having alarge incident angle is applied to this type of screen, most of thelight reflected by the screen travels in a direction having a largeangle with respect to the normal line of the incident surface. In thiscase, an image observed from the front of the screen does not havesufficient brightness. Moreover, the related-art screen which reflectsnot only light coming from the projector but also outside light asunnecessary light with high reflectance cannot obtain sufficientcontrast in many cases. Particularly, under the environment containing aconsiderable amount of outside light, the light quantity of the suppliedprojection light needs to increase. According to the related-arttechnology, therefore, it is difficult to produce an image having highbrightness and high contrast when the image is displayed on a largescreen from a short projection distance.

SUMMARY

It is an advantage of some aspects of the invention to provide a screenused to produce an image having high contrast and high brightness whenthe image is displayed on a large screen from a short projectiondistance, and to provide a projection system using this screen.

A screen according to a first aspect of the invention includes aplurality of convexes disposed on a flat surface with a clearance leftbetween one another. The convexes reflect diagonal incident light comingin a predetermined direction other than the normal line direction of theflat surface, and block the diagonal incident light by reflecting theincident light such that the incident light cannot reach each areabetween the adjoining convexes on the flat surface.

When the direction of the diagonal incident light reaching the convexesis a predetermined direction, the diagonal incident light cannot reachthe area between the adjoining convexes. Since the diagonal incidentlight has a large incident angle, a beam having passed through thevicinity of one convex can be directed toward another convex positionednext to the one convex. While the related-art screen reflects light bythe entire surface of the screen, the screen according to this aspect ofthe invention has angle selectivity which allows the diagonal incidentlight to be efficiently reflected. The convexes may have a structurewhich allows the diagonal incident light to travel in a desireddirection. Thus, light in accordance with an image signal canefficiently advance toward the audience during close projection,producing a bright image for display. Moreover, since the diagonalincident light is efficiently reflected, reflection of outside lightcoming in a direction different from that of the light according to theimage signal can be reduced. By the reduction of the outside lightreflection, high contrast can be obtained. Accordingly, a screen used toproduce an image having high contrast and high brightness when the imageis displayed on a large screen from a short projection distance can beprovided.

It is preferable that each of the convexes has a reflection portionwhich reflects the diagonal incident light. In this structure, thediagonal incident light reaching the convexes can be efficientlyreflected.

It is preferable that a substrate which has the flat surface andtransmits light, and an anti-reflection member provided on the side ofthe substrate opposite to the side having the convexes to reducereflection of light are further included. The anti-reflection memberreduces reflection of outside light having passed through the substrate.Thus, reflection of the outside light can be reduced.

It is preferable that an anti-reflection member provided between theadjoining convexes to reduce reflection of light is further included.The anti-reflection member reduces reflection of outside light reachingthe areas between the adjoining convexes on the flat surface. In thisstructure, reflection of the outside light can be reduced.

It is preferable that the convexes diffuse the diagonal incident light.In this structure, preferable visibility angle characteristics can beobtained.

It is preferable that the convexes are so shaped as to have thelongitudinal direction corresponding to a first direction, and arearranged in a second direction orthogonal to the first direction. Inthis structure, the diagonal incident light can be reflected in adesired direction. Moreover, an image having uniform brightness can beeasily obtained, and manufacture can be simplified.

It is preferable that each of the convexes has a curved surface in thefirst direction and substantially flat having a curvature in the seconddirection. In this case, the diagonal incident light can be diffused.

It is preferable that the convexes are arranged in both the firstdirection and the second direction orthogonal to the first direction. Inthis structure, the diagonal incident light can be reflected in adesired direction. Moreover, the convexes can be disposed with randompatterns. Since the arrangement patterns of the convexes are random,moiré effect can be reduced.

It is preferable that each of the convexes has a curved surface havingcurvatures in both the first direction and the second direction. In thiscase, the diagonal incident light can be diffused.

It is preferable that the convexes are disposed substantially concentricwith one another. In this structure, the reflectivity characteristics ofthe screen can be equalized, and an image having a uniform brightnesscan be obtained.

It is preferable that the convexes are disposed along circular arcs eachof which has a substantially equal radius. In this structure,reflectivity characteristics similar to those obtained when the convexesare disposed substantially concentric with one another can be acquired.Moreover, since a sheet-shaped member embossed or processed by othermethods is freely cut for use, reduction of the manufacturing cost canbe achieved.

It is preferable that the convexes are formed by an ink jet method. Inthis case, the convexes disposed with complex patterns can be easilyproduced. Moreover, since no mold is used, various types of products canbe easily manufactured.

It is preferable that the convexes are formed by embossing. In thiscase, the convexes can be easily formed, and thus reduction of themanufacturing cost can be achieved.

A projection system according to a second aspect of the inventionincludes a projection engine unit which projects light in accordancewith an image signal, and a screen which receives light emitted from theprojection engine unit. The screen has a plurality of convexes disposedon a flat surface with a clearance left between one another. Theprojection engine unit applies light to the screen in a predetermineddirection other than the normal line direction of the flat surface. Theconvexes reflect light emitted from the projection engine unit and blockthe light from the projection engine unit by reflecting the light suchthat the light cannot reach each area between the adjoining convexes onthe flat surface. In this structure, a projection system used to producean image having high contrast and high brightness when the image isdisplayed on a large screen from a short projection distance can beobtained.

It is preferable that each of the convexes has a reflection portionwhich reflects the light emitted from the projection engine unit.Reflectance of the reflection portion when reflecting the light emittedfrom the projection engine unit is higher than when reflecting lighthaving a wavelength range other than the wavelength range of the lightemitted from the projection engine unit. In this structure, wavelengthselectivity which allows the light emitted from the projection engineunit to be efficiently reflected is obtained. Thus, light in accordancewith the image signal can be efficiently reflected, and reflection ofoutside light can be reduced. Accordingly, an image having highercontrast and brightness can be displayed.

It is preferable that the projection engine unit and the screen aredisposed in such positions that the optical axes of the projectionengine unit and the screen coincide with each other. Each of theconvexes is disposed substantially concentric with one another with thecenter of the concentric circle located at the cross point of anextension surface of the flat surface and the optical axis or in thevicinity of the cross point. In this structure, the reflectivitycharacteristics of the screen can be equalized, and an image havinguniform brightness can be obtained.

It is preferable that the convexes are disposed with a pitch smallerthan a pitch of pixels formed by light in accordance with the imagesignal. In this case, lowering of resolution can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers refer to like elements.

FIG. 1 schematically illustrates a structure of a projection systemaccording to a first embodiment of the invention.

FIG. 2 schematically illustrates a structure of an optical engine.

FIG. 3 shows an optical system of the projection system.

FIG. 4 is a cross-sectional view showing a structure of a main part of ascreen.

FIG. 5 is a plan view showing a structure of the screen.

FIG. 6 is a cross-sectional view showing a structure of a convex.

FIG. 7 shows the relationship between the convex structure and pixelsize.

FIG. 8 shows reflection characteristics of a reflection portion.

FIG. 9 illustrates a convex in a modified example.

FIG. 10 illustrates a convex in another modified example.

FIG. 11 is a plan view showing a structure of a screen having dot-shapedconvexes.

FIG. 12 is a cross-sectional view showing a structure of a convex.

FIG. 13 shows the relationship between the convex structure and pixelsize.

FIG. 14 illustrates a structure having convexes disposed along circulararcs each of which has a substantially equal radius.

FIG. 15 illustrates a structure having convexes formed by deforming asheet-shaped member.

FIG. 16 illustrates another structure having convexes formed bydeforming a sheet-shaped member.

FIG. 17 shows an embossing method which uses a roll mold.

FIG. 18 schematically illustrates a structure of a projection systemaccording to a second embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments according to the invention are hereinafter described indetail with reference to the drawings.

First Embodiment

FIG. 1 schematically illustrates a structure of a projection system 10according to a first embodiment of the invention. The projection system10 includes a projection engine unit 11 and a screen 12. The projectionengine unit 11 is a front projection type projector which projects lightin accordance with an image signal. The projection engine 11 achievesclose projection from a position within 1 meter such as about 30centimeters from a wall surface W on which the screen 12 is attached.The screen 12 is a reflection type screen which reflects light emittedfrom the projection engine unit 11. The projection engine unit 11 has anoptical engine 13, a projection lens 14, and an aspherical surfacemirror 15.

FIG. 2 schematically illustrates the structure of the optical engine 13.An LED 21R for red (R) light as a solid light source is a light sourceunit for supplying R light. The R light emitted from the LED 21R for Rlight and collimated by a collimator lens 22 enters a spatial lightmodulating device 23R for R light. The spatial light modulating device23R for R light is a transmission type liquid crystal device whichmodulates R light according to an image signal. The R light modulated bythe spatial light modulating device 23R for R light enters a crossdichroic prism 24 as a color synthesis optical system.

An LED 21G for green (G) light as a solid light source is a light sourceunit for supplying G light. The G light emitted from the LED 21G for Glight and collimated by the collimator lens 22 enters a spatial lightmodulating device 23G for G light. The spatial light modulating device23G for G light is a transmission type liquid crystal device whichmodulates G light according to an image signal. The G light modulated bythe spatial light modulating device 23G for G light enters the crossdichroic prism 24 from a side different from the side from which the Rlight enters the cross dichroic prism 24.

An LED 21B for blue (B) light as a solid light source is a light sourceunit for supplying B light. The B light emitted from the LED 21B for Blight and collimated by the collimator lens 22 enters a spatial lightmodulating device 23B for B light. The spatial light modulating device23B for B light is a transmission type liquid crystal device whichmodulates B light according to an image signal. The B light modulated bythe spatial light modulating device 23B for B light enters the crossdichroic prism 24 from a side different from the sides from which the Rlight and the G light enter the cross dichroic prism 24. The opticalengine 13 may use an equalizing optical system which equalizes lightintensity distribution such as rod integrator and fly-eye lens.

The cross dichroic prism 24 has a first dichroic film 25 and a seconddichroic film 26 as two dichroic films crossing each other substantiallyat right angles. The first dichroic film 25 reflects R light andtransmits G and B lights. The second dichroic film 26 reflects B lightand transmits R and G lights. The cross dichroic prism 24 synthesizes R,G and B lights entering from different sides, and releases thesynthesized light toward the projection lens 14. The projection lens 14projects the light synthesized by the cross dichroic prism 24.

The transmission type liquid crystal display device is constituted by ahigh temperature polysilicon (HTPS) TFT liquid crystal panel, forexample. The spatial light modulating device included in the opticalengine 13 is not limited to the transmission type liquid crystal displaydevice, but may be a reflection type liquid crystal display device(liquid crystal on silicon; LCOS), DMD (digital micromirror device), GLV(grating light valve), and other devices. In addition, the spatial lightmodulating device need not be equipped for each color, but may be astructure for modulating light by color sequential system whichsequentially supplies respective color lights to a common spatial lightmodulating device. The light source units included in the optical engine13 are not limited to LEDs, but may be solid light sources other thanLEDs or lamps such as extra-high pressure mercury lamp.

Returning to FIG. 1, the aspherical surface mirror 15 is disposed insuch a position as to be opposed to the projection lens 14. Theaspherical surface mirror 15 has a curved surface having an asphericalsurface shape. The aspherical surface mirror 15 widens the angle of thelight coming from the projection lens 14 chiefly in the horizontaldirection by reflection. The aspherical surface mirror 15 also folds thelight from the projection lens 14 such that the light travels toward anemission portion 16. The aspherical surface mirror 15 is produced byforming a reflection film on a substrate which has resin material or thelike, for example. The reflection film is a layer of highly reflectivematerial, for example, including a layer of metal material such asaluminum and a dielectric multi-layer film. It is possible to provide aprotection film having transparent material on the reflection film. Theaspherical surface mirror 15 which has a curved surface shape performsboth folding of light and widening of light angle at the same time.Since the light angle is widened not only by the projection lens 14 butalso by the aspherical surface mirror 15, size reduction of theprojection lens 14 can be achieved more than the structure where thelight angle is widened only by the projection lens 14. The shape of theaspherical surface mirror 15 may be modified into an appropriate shapewhich can correct image distortion.

The aspherical surface mirror 15 is disposed such that a part of theaspherical surface mirror 15 projects out of a housing 17. The emissionportion 16 through which light coming from the aspherical surface mirror15 to the outside of the housing 17 is a portion surrounded by anopening formed on the housing 17 and the aspherical surface mirror 15.The projection engine unit 11 may be constructed such that therespective components from the optical engine 13 to the asphericalsurface mirror 15 are completely accommodated in the housing 17. Amirror for folding the optical path may be further provided between theprojection lens 14 and the aspherical surface mirror 15. The projectionengine unit 11 is installed on a floor surface, a desk, or a side board,for example. The projection engine unit 11 having a compact structurecan easily secure an appropriate installation place.

FIG. 3 illustrates an optical system of the projection system 10. Therespective components of the optical engine 13, the projection lens 14,the aspherical surface mirror 15, and the screen 12 constitute aso-called co-axial optical system having a common optical axis AX. Theoptical engine 13, the projection lens 14, the aspherical surface mirror15, and the screen 12 also forms a so-called shift optical system whichshifts light emitted from the optical engine 13 from the optical axis AXto a particular side such that the light advances toward the particularside. By this structure, the projection engine unit 11 supplies lighthaving a large incident angle to the screen 12. The incident angle is anangle formed between the normal line N of the screen 12 and an incidentlight beam. The light emitted from the projection engine 11 is adiagonal incident light reaching in a predetermined direction other thanthe direction of the normal line N of the screen 12. The normal line Nof the screen 12 corresponds to a normal line of a flat surface whichwill be described later.

The projection system 10 having the co-axial optical system can useordinary coaxial design methods. Thus, both the number of designingprocesses for the optical system and aberration produced in the opticalsystem can be decreased. The aspherical surface mirror 15 may have asubstantially rotation-symmetric shape with respect to the optical axisAX such as a shape of a part other than the top cut from a circularcone. Since the aspherical surface mirror 15 has a substantiallyrotation-symmetric shape with respect to the optical axis AX, theoptical axis of the aspherical surface mirror 15 can be easily alignedwith the optical axes of other structures. Moreover, the asphericalsurface mirror 15 having an axis-symmetric aspherical surface shape canbe processed by simple methods such as lathing. Thus, the asphericalsurface mirror 15 can be easily and highly accurately manufactured.

The projection system 10 having the projection lens 14 and theaspherical surface mirror 15 employs extra-wide-angle optical systemhaving a wide angle θ of at least 150 degrees such as 160 degrees. Sincethe projection system 10 adopts the shift optical system which uses onlya part of an angle range of highly widened light, equalization of thelight traveling direction can be achieved. The angle of light reachingthe screen 12 from the projection engine unit 11 lies within apredetermined angle range not including the direction of the normal lineN of the screen 12. According to this embodiment, the minimum incidentangle is 70 degrees and the maximum incident angle is 80 degrees withrespect to the screen 12. Since the shift optical system is employed,the angle difference of lights reaching the screen 12 can be decreasedto 10 degrees or smaller.

FIG. 4 is a cross-sectional view of a main part of the screen 12. Asubstrate 31 is a plastic sheet or other types of parallel flat platemade of transparent material such as resin. The substrate 31 transmitslight. The substrate 31 has a plurality of convexes 32 on a flat surfaceS on the light entrance side. The respective convexes 32 are disposedwith a clearance left between one another. The cross section shown inthe figure contains the normal line N of the flat surface S and theoptical axis AX (not shown). Each of the convexes 32 has across-sectional shape as a part of a circle cut by a straight line.

FIG. 5 is a plan view showing the structure of the screen 12 as viewedfrom the light entrance side. The convexes 32 are disposed substantiallyconcentric with one another. The centers of the concentric circles ofthe convexes 32 are positioned at a cross point of a surface extendingfrom the flat surface S and the optical axis AX. Each of the convexes 32has a shape whose longitudinal direction corresponds to a directionalong a circular arc of a circle whose center is located at the opticalaxis AX. The direction along the circular arc of the circle whose centeris located at the optical axis AX corresponds to a first direction. Theconvexes 32 are disposed in a direction along a radius of the circlewhose center is located at the optical axis AX. The direction along theradius of the circle whose center is located at the optical axis AXcorresponds to a second direction orthogonal to the first direction. Thecenter of the concentric circle of each convex 32 may be located at aposition near the cross point of the surface extending from the flatsurface S and the optical axis AX. Each of the convexes 32 has a curvedsurface which is substantially flat in the first direction and has acurvature in the second direction.

FIG. 6 is a cross-sectional view showing the structure of each convex32. The convex 32 has a reflection portion 36 covering the substrate 35.At the reflection portion 36, the convex 32 reflects light emitted fromthe projection engine unit 11 (see FIG. 1). The substrate 35 is producedby using resin material such as ultraviolet ray hardening resin andfoaming ink. The reflection portion 36 contains highly reflectivematerial. The reflection portion 36 is produced by applying whitepainting or silver painting. The convex 32 having a curved surface candiffuse light emitted from the projection engine unit 11. The crosssection shown in the figure crosses the first direction at right angles.The convex 32 has substantially the same cross-sectional structure shownin the figure at any position in the first direction. Thecross-sectional structure of the convex 32 is not limited to a shapeequivalent to a part of a circle, but may be a shape equivalent to apart of an ellipse or other shapes. The convex 32 may be formed byforming the reflection portion 36 on the substrate 35 or may be producedby using other highly reflective materials such as milky(semi-transparent) materials.

Light coming from the projection engine unit 11 can be reflected towardthe front of the screen 12 by the convexes 32 having the abovestructure. Since the convexes 32 are arranged substantially concentricwith one another, the light from the projection engine unit 11 can beuniformly reflected by the screen 12. Thus, the reflectivecharacteristics of the screen 12 are equalized, and an image havinguniform brightness can be obtained. Since the convexes 32 having thelongitudinal direction are formed, an image having uniform brightnesscan be easily produced. Moreover, the convexes 32 having thelongitudinal direction can be manufactured by a simplified method.

FIG. 7 shows the relationship between the structure of the convexes 32and the size of pixels 40. The convexes 32 are disposed with a pitchsmaller than that of the pixels 40 formed on the screen 12 by the lightsupplied from the projection engine unit 11. It is preferable that theplural convexes 32 are contained in one pixel 40. When a side d of apixel is 0.7 mm, for example, a pitch p of the convexes 32 is 0.14 mm.In this case, five convexes 32 are contained in one pixel 40. Since theconvexes 32 are arranged with the pitch p smaller than the pitch of thepixels 40, lowering of resolution can be reduced. It is preferable thatthe pitch p of the convexes 32 is one fifth of the pitch of the pixels40 or smaller.

Returning to FIG. 4, an anti-reflection member 33 is provided on thewall surface W (see FIG. 1) of the substrate 31 opposite to the sidewhere the convexes 32 are provided. The anti-reflection member 33 coversthe entire area of the wall surface W of the substrate 31. Theanti-reflection member 33 absorbs light having passed through thesubstrate 31 to reduce reflection of the light having passed through thesubstrate 31. The anti-reflection member 33 contains light absorbingmaterial. The anti-reflection member 33 is produced by applying matblack painting, for example.

Light L1 emitted from the projection engine unit 11 and reflected by theconvexes 32 diffuses within a predetermined range around the normal lineN. Thus, preferable visibility angle characteristics can be obtained.Since the light L1 coming from the projection engine unit 11 has a largeincident angle, a beam r having passed through the vicinity of oneconvex 32 a reaches another convex 32 b positioned next to the oneconvex 32 a, for example. Thus, the light L1 from the projection engineunit 11 is reflected only by the convexes 32 of the screen 12.Accordingly, the screen 12 can be so designed as to reflect the light L1coming from the projection engine unit 11 only by the convexes 32 byappropriately determining the heights and intervals of the convexes 32.

Since the light L1 emitted from the projection engine unit 11 entersdiagonally from a predetermined direction, shadows of the convexes 32are cast on the flat surface S at the areas between the adjoiningconvexes 32. The convexes 32 constructed to reflect the light L1 comingfrom the projection engine unit 11 block the light L1 such that thelight L1 cannot reach the areas between the adjoining convexes 32 on theflat surface S. Outside light L2 having passed through the flat surfaceS in the areas between the adjoining convexes 32 passes through thesubstrate 31 and reaches a rear anti-reflection member 33. The rearanti-reflection member 33 absorbs the outside light L2 to reducereflection of the outside light L2. The rear anti-reflection member 33can reduce reflection of the outside light L2 reaching the areas betweenthe adjoining convexes 32 at any angles.

According to this embodiment, angle selectivity for efficientlyreflecting the light L1 emitted from the projection engine unit 11 canbe obtained. Moreover, the light L1 from the projection engine unit 11can be efficiently directed toward the audience. Thus, light accordingto an image signal can travel toward the audience with high efficiencyduring close projection, allowing a bright image to be displayed.Moreover, contrast increases by reducing reflection of the outside lightL2, providing an advantage that a high-contrast and bright image can bedisplayed on a large screen from a short projection distance. Since theamount of the projection light need not be increased even under theenvironment containing a plenty of the outside light L2, reduction ofpower consumption can be achieved.

It is now assumed that the following conditions have been established.The reflectance of the convexes 32 is 80%. The reflectance of theanti-reflection member 33 is 9%. The area ratio of the region having theconvexes 32 to the region other than the region having the convexes 32in the flat surface S is 1:3. Since the light L1 emitted from theprojection engine unit 11 only reaches the convexes 32, the averagereflectance for the reflection of the light L1 coming from theprojection engine unit 11 is 80%. The outside light L2 uniformly reachesthe entire area of the flat surface S. The average reflectance for thereflection of the outside light L2 is calculated by the equation:80%×0.25+9%×0.75=26.75%.

Thus, the screen 12 can decrease the effect of the outside light L2 toabout one third of the effect of the light L1 coming from the projectionengine unit 11. For example, a projector having a lighted room contrastof 100:1 under a certain condition can obtain contrast of about 300:1.

The convexes 32 may have a structure which exhibits higher reflectancewhen reflecting the light L1 from the projection engine unit 11 thanthat when reflecting light having a wavelength range other than thewavelength range of the light L1 from the projection engine unit 11. Thereflection portion 36 can be produced by using color material havingwavelength selectivity for selectively reflecting the light L1 comingfrom the projection engine unit 11. It is herein assumed that therespective color lights emitted from the LED 21R for red (R) light, theLED 21G for green (G) light, and the LED 21B for blue (B) light (seeFIG. 2) of the optical engine 13 have wavelength ranges indicated by R,G, and B shown in FIG. 8, respectively. In this figure, the horizontalaxis indicates wavelength, the left vertical axis indicates relativeintensity, and the right vertical axis indicates reflectance of thereflection portion 36. As shown by a bold line in the figure, thereflection portion 36 has such reflection characteristics that exhibithigh reflectance such as about 100% in the vicinity of the respectivepeak wavelengths in the R, G and B ranges.

The screen 12 having this wavelength selectivity can efficiently reflectthe light L1 coming from the projection engine unit 11 and reducereflection of the outside light L2. Thus, a further high contrast andbright image can be displayed. For providing the wavelength selectivityof the screen 12, color lights having wavelength ranges limited to someextent need to be supplied from a light source unit. Thus, the structurecapable of providing wavelength selectivity of the screen 12 isappropriately used in combination with a solid light source or a laserbeam source which can supply color lights having narrow wavelengthranges.

It is preferable that the anti-reflection member 33 can reducereflection of lights having as broad wavelength ranges as possible. Theoutside light L2 such as sunray, light from a fluorescent lamp, andlight from an incandescent lamp has a relatively wide wavelength range.Since the anti-reflection member 33 capable of reducing reflection oflights having wide wavelength ranges is used, reflection of the outsidelight L2 can be effectively decreased. In such a case where the outsidelight L2 having a wavelength range limited to some extent enters, theanti-reflection member 33 may have wavelength selectivity correspondingto the wavelength characteristics of the outside light L2.

FIGS. 9 and 10 illustrate modified examples of the convex. While theconvex 32 discussed above (see FIG. 6) has the reflection portion 36provided on the entire curved surface, a convex 41 shown in FIG. 9 has areflection portion 42 provided on a part of the curved surface. Thereflection portion 42 is disposed on the area receiving the light L1from the projection engine unit 11. Thus, the reflection portion 42guides the outside light L2 entering the area other than the area havingthe reflection portion 42 on the convex 41 toward the anti-reflectionmember 33, and further reduces reflection of the outside light L2.Moreover, the reflection portion 42 requires a smaller amount of whitepainting or the like at the time of production of the reflection portion42.

A convex 44 shown in FIG. 10 has a cross section of an isoscelestriangle shape. A reflection portion 46 is provided on a surface of asubstrate 45 on the side receiving the light L1 from the projectionengine 11. The reflection portion 46 having small convexes and concavesreflects the light L1 coming from the projection engine unit 11 and alsodiffuses the light L1 on the audience side. Thus, preferable visibilityangle characteristics can be obtained. Similar small concaves andconvexes may be formed on the reflection portions 36 and 42 of theconvexes 32 and 41. The cross-sectional shapes of the convexes are notlimited to the shapes discussed in these specific examples, butappropriate modifications may be given to those. For example, thecross-sectional shapes of the convexes may be rectangular shapes orpolygonal shapes.

FIG. 11 is a plan view showing a structure of a screen 50 havingdot-shaped convexes 51. Each of the convexes 51 is disposed in adirection along a circular arc of a circle whose center is located atthe optical axis AX, and in a direction along a radius of a circle whosecenter is located at the optical axis AX. The direction along thecircular arc of the circle whose center is located at the optical axisAX corresponds to the first direction. The direction along the radius ofthe circle whose center is located at the optical axis AX corresponds tothe second direction orthogonal to the first direction. The convexes 51are provided on the entire surface of the screen 50. Here, a part of theconvexes 51 are not shown in the figure. Each of the convexes 51 has ashape as a part of a spherical surface cut by a flat surface. Each ofthe convexes 51 has a curved surface having curvature in both the firstand second directions.

The screen 50 having the convexes 51 arranged substantially concentricwith one another can uniformly reflects the light coming from theprojection engine unit 11. The convexes 51 are disposed substantially atthe constant intervals in the concentric direction. The convexes 51 arealternately positioned with respect to the adjoining circular arcs. Theconvexes 51 are disposed substantially at the constant intervals also inthe radial directions of the concentric circle. One convex 51 isprovided on every two circular-arc lines in the radial direction of theconcentric circle. In this structure, the arrangement pattern of thedot-shaped convexes 51 can be provided with randomicity. Since thearrangement pattern of the convexes 51 is random, moiré effect can bedecreased.

FIG. 12 illustrates a cross-sectional structure of the convex 51. Theconvex 51 having the cross-sectional structure shown in the figure has across-sectional shape as a part of a circle cut by a straight line. Theconvex 51 has a substrate 52 and a reflection portion 53. The structureof the convex 51 has a structure similar to that of the convex 32discussed above (see FIG. 6) except for a different shape. The convex 51has the same structure on any cross sections including the center line.By the presence of the convex 51, the light coming from the projectionengine unit 11 can be reflected toward the front of the screen 12. Sincethe convex 51 has a curved surface having curvatures in two directions,the light from the projection engine unit 11 can be diffused in twodirections. The cross-sectional structure of the convex 51 is notlimited to a shape equivalent to a part of a circle, but may be a shapeequivalent to an ellipse or other shapes.

FIG. 13 shows the relationship between the structure of the convexes 51and the size of the pixels 40. The convexes 51 are disposed with a pitchsmaller than that of the pixels 40. It is preferable that the pluralconvexes 51 are contained in one pixel 40. When one side d of the pixelis 0.7 mm, for example, a pitch p of the convexes 51 is 0.14 mm. In thiscase, thirty convexes 51 are contained in one pixel 40. By disposing theconvexes 51 with the pitch p smaller than the pitch of the pixels 40,lowering of resolution can be reduced. The pitch p of the convexes 51 ispreferably one fifth of the pitch of the pixels 40 or smaller.

The convexes according to these examples can be produced by using an inkjet method or a screen printing method. When the ink jet method is used,the convexes arranged with complex patterns can be easily formed. Whenthe ink jet method requiring no mold is employed, various types ofproducts can be easily manufactured. The screen printing method isappropriate for mass production of screens. Since the plastic sheet usedfor the substrate 31 (see FIG. 4) has a smooth surface, the convexes canbe easily formed. Moreover, the plastic sheet used as the substrate 31can transmit light.

The structure of the screen is not limited to the structure having theconvexes arranged substantially concentric with one another. Forexample, a screen 54 having convexes 55 disposed along circular arcseach of which has a substantially equal radius may be used. The convexes55 have the longitudinal direction corresponding to the first direction.The convexes 55 disposed along the circular arcs having a substantiallyequal radius have a structure similar to that of the convexes arrangedsubstantially concentric with one another, and therefore can providereflectivity characteristics similar to those of the convexes arrangedsubstantially concentric with one another. Each of the convexes 55 maybe positioned along a part of a substantially equal ellipse. The shapesof the convexes 55 are not limited to those having the longitudinaldirection corresponding to the first direction, but may be dot-shapedsimilarly to the convexes 51 discussed above (see FIG. 11).

The convexes of the screen are not limited to those provided on thesubstrate, but may be convexes produced by deforming a sheet-shapedmaterial. For example, a screen 60 shown in FIG. 15 has convexes 61produced by deforming a sheet-shaped member 62. The sheet-shaped member62 is deformed by embossing, for example. The sheet-shaped member 62 isa light absorbing material such as a sheet colored with black painting,for example.

The convexes 61 are formed by applying white painting, color materialhaving wavelength selectivity, or other paintings to areas of thesheet-shaped member 62 raised by deformation. The convexes 61 have thelongitudinal direction corresponding to the first direction similarly tothe convexes 32 discussed above (see FIG. 5). The convexes 61 havecurved surfaces similar to those of the convexes 32 (see FIG. 6). Thelight emitted from the projection engine unit 11 can be efficientlyreflected by the convexes 61. The shapes of the convexes 61 are notlimited to those having the longitudinal direction corresponding to thefirst direction, but may be dot-shaped similarly to the convexes 51discussed above (see FIG. 11).

Each area between the adjoining convexes 61 on the sheet-shaped member62 absorbs outside light. Each area between the adjoining convexes 61 onthe sheet-shaped member 62 functions as an anti-reflection member.Accordingly, reflection of outside light can be reduced by thesheet-shaped member 62, and therefore a high-contrast and bright imagecan be displayed. The screen 60 may have a substrate for supporting thesheet-shaped member 62, for example, in addition to the sheet-shapedmember 62.

The substrate 31 of the screen 12 shown in FIG. 4 may also beconstituted by a light absorbing material. In this case, each areabetween the adjoining convexes 32 on the substrate 31 functions as ananti-reflection member. The anti-reflection function of the substrate 31allows display of a high-contrast and bright image. The anti-reflectionfunction of the substrate 31 also eliminates the necessity for applyinglight absorbing material to the wall surface W side surface of thesubstrate 31.

A screen 65 shown in FIG. 16 has convexes 66 produced by deforming asheet-shaped member 64 in a similar manner to the case of the screen 60shown in FIG. 15. The sheet-shaped member 64 is a material having highreflectivity such as a sheet colored with white painting, for example.The raised portions of the sheet-shaped member 62 can be used as theconvexes 61. Each area between the adjoining convexes 61 on thesheet-shaped member 64 has an anti-reflection member 67. Theanti-reflection member 67 is produced by applying mat black painting,for example. This structure allows display of a high contrast and brightimage similarly to the above example.

Each area of the adjoining convexes 32 on the flat surface S of thescreen 12 shown in FIG. 4 may also have the anti-reflection member. Inthis case, reflection of the outside light reaching the area between theadjoining convexes 32 can be reduced similarly to the above example. Inaddition, the necessity for applying light absorbing material to thewall surface W side surface of the substrate 31 can be eliminated. Forforming the anti-reflection member on the flat surface S, the substrate31 may be constituted by an opaque material such as paper and clothinstead of a transparent material.

Embossing capable of easily forming convexes is useful for massproduction of screens. When embossing is used to produce convexes, aroll mold 68 having concaves and convexes shown in FIG. 17 may be used.By rolling the roll mold 68 while pressing it against a sheet-shapedmember 69, convexes can be easily produced. In case of the structurehaving the convexes disposed along circular arcs each of which has asubstantially equal radius, the embossed sheet member 69 can be freelycut for use. In this case, the manufacturing cost can be reduced byusing the embossing method. The roll mold 68 can be applied to eitherthe convexes which have the longitudinal direction corresponding to thefirst direction, or the dot-shaped convexes.

Second Embodiment

FIG. 18 schematically illustrates a projection system 70 according to asecond embodiment of the invention. The projection system 70 in thisembodiment has an upside-down structure of that of the projection system10 in the first embodiment. The projection system 70 in this embodimentprojects light from vertically above a screen 72. The projection engineunit 11 is suspended from a ceiling surface, for example. The projectionengine unit 11 used in the first embodiment is disposed upside down inthis embodiment.

The screen 72 has the upside-down structure of the screen 12 used in thefirst embodiment. According to this embodiment, a high contrast andbright image can be displayed during close projection similarly to thefirst embodiment. The structure of the projection system is not limitedto the upside-down structure of the projection system 10 in the firstembodiment, but may be a structure rotated through 90 degrees. Thescreens in the respective embodiments are not limited to those used incombination with a particular projection engine unit to constitute aprojection system, but may be used with any types of projector.

Accordingly, the screen according to these embodiments are usefulparticularly when used in combination with a projector which projectslight from a position close to a screen.

The entire disclosure of Japanese Patent Application NOs: 2006-279506,filed Oct. 13, 2006 and 2007-203867, filed Aug. 6, 2007 are incorporatedby reference herein.

1. A screen, comprising: a plurality of reflecting portions disposedalong circular arcs with a clearance left between one another, each ofthe reflecting portions has a curved surface having curvatures in bothfirst direction and second direction orthogonal to the first direction,and reflects diagonal incident light coming in a predetermined directionother than the normal line direction of the screen.
 2. The screenaccording to claim 1, further comprising: a substrate which has a flatsurface and transmits light; and an anti-reflection member provided onthe side of the substrate opposite to the side having the reflectingportions to reduce reflection of light.
 3. The screen according to claim1, further comprising an anti-reflection member provided between theadjoining reflecting portions to reduce reflection of light.
 4. Thescreen according to claim 1, wherein the reflecting portions diffuse thediagonal incident light.
 5. The screen according to claim 1, whereineach of arcs has a substantially equal radius.
 6. A projection system,comprising: the screen according to claim 1, and a projection engineunit which projects light in accordance with an image signal, theprojection engine unit applies light to the screen in a predetermineddirection other than the normal line direction of the screen.
 7. Theprojection system according to claim 6, wherein: each of the reflectingportions reflects the light emitted from the projection engine unit; andreflectance of the reflection portion when reflecting the light emittedfrom the projection engine unit is higher than when reflecting lighthaving a wavelength range other than the wavelength range of the lightemitted from the projection engine unit.
 8. The projection systemaccording to claim 6, wherein the reflecting portions are disposed witha pitch smaller than a pitch of pixels formed by light in accordancewith the image signal.